1. Field of the Invention
The present invention relates to an antenna, and in particular to a relatively compact patch antenna assembly.
2. Description of Prior Art
Nowadays, automotive satellite navigation systems rapidly become more and more popular. In addition to be combined with an in-car AV system, many kinds of GPS products are developed in which the satellite navigation system is integrated with a PDA, Notebook or mobile phone. The GPS product which is most closely related to the car owner is the portable automobile GPS. As to the car owner whose car is not originally equipped with a GPS, it is good for him/her to choose a portable automobile GPS because the price thereof is reasonable and the portability thereof allows to be used out of the car. Further, even the car owner buys a new car in the future, he/she can still use this portable automobile GPS.
When the GPS is integrated with various electronic products such a PDA, Notebook or mobile phone, a GPS signal-receiving antenna assembly is necessarily built in the electronic device. With reference to FIG. 1, the antenna comprises a substrate 1A, a radiation metal pieces 2A, a grounded metal pieces 3A and a signal-inputting body 4A. The substrate of this kind of antenna is made of ceramic materials having a high dielectric constant (8-150). The resonant frequency of the circularly polarized patch antenna is 1575.42 MHz.
Recently, since the volume of the PDA or mobile phone is made more and more compact, when the GPS is to be integrated with the PDA or mobile phone, a phenomenon may occurs that the existing circularly polarized patch antenna shown in FIG. 1 cannot be mounted therein. Moreover, it is difficult for this kind of circularly polarized patch antenna to further reduce the size thereof because the area of the radiation metal piece 2A connected on the surface of the substrate 1A will be reduced accordingly when the volume of the substrate 1A is reduced. On the condition that the substrate dielectric constant is not changed, once the area of the radiation metal piece 2A is reduced, the resonant frequency of the antenna will rise to depart from the frequency band that can be received by the GPS, which causes the GPS unable to receive the signals. Although the antenna can be mounted in a small-volume PDA or mobile phone, the function of receiving satellite signals may not be obtained. Therefore, it is an important issue in the field of the present invention to reduce the area and volume of the circularly polarized patch antenna.